Conventionally, various light emitting elements have been known which emit light when radiation or light enters the elements. Specific examples of such light emitting elements include, for example, wavelength conversion elements which emit light of a longer wavelength than that of incident ultraviolet light when ultraviolet light or the like enters the elements, and radiation-to-light conversion elements which emit fluorescence when radiation enters the elements.
For example, radiation-to-light conversion elements are used for scintillators which are radiation detectors. The radiation-to-light conversion elements for use in scintillators, etc. are required to be high in luminescent efficiency and short in emission decay time, in order to increase the spatial resolutions and temporal resolutions of the scintillators. Examples of the radiation-to-light conversion elements which satisfy these requirements include radiation-to-light conversion elements which use a single crystalline material as described in, for example, Patent Documents 1 and 2 below.
In addition, Patent Document 3 below discloses a ceramic scintillator containing an oxysulfide or an oxide containing a rare earth.